I've recently just put a z6 head on my friends y7 block with a2 pistons. Everything was honed and check including the piston rings and everything is within spec but when he gets on it the spark plug wires are popping out. We've tried re-torquing them and used thread sealer but they still keep popping out. Any help would be great.

 

you have excessive crankcase pressure.. the blowby needs somewhere to go.

IDK if your block has plugs on the backk like a bseries, but that is usually the way its done.

You can tap the valvecover and run larger lines to a vented can.

Dont drive WOT till this gets done or youll be replacing the rings sooner then u think.